<template>
    <el-checkbox :indeterminate="isIndeterminate" v-model="checkAll" @change="handleCheckAllChange">全选</el-checkbox>
    <div style="margin: 15px 0;"></div>
    <el-checkbox-group v-model="checkedCities" @change="handleCheckedCitiesChange">
        <el-checkbox v-for="city in cities" :label="city" :key="city">{{city}}</el-checkbox>
    </el-checkbox-group>
</template>

<script>
    const cityOptions = ['上海', '北京', '广州', '深圳'];
    export default {
        name: "testCheckbox",
        data() {
            return {
                checkAll: false,
                checkedCities: ['上海', '北京'],
                cities: cityOptions,
                isIndeterminate: true
            };
        },
        methods: {
            handleCheckAllChange(val) {
                this.checkedCities = val ? cityOptions : [];
                this.isIndeterminate = false;
            },
            handleCheckedCitiesChange(value) {
                let checkedCount = value.length;
                this.checkAll = checkedCount === this.cities.length;
                this.isIndeterminate = checkedCount > 0 && checkedCount < this.cities.length;
            },
        }
    }


</script>

<style scoped>

</style>